Considerations for the applying of high-temperature coatings – Part 1

Managers of petrochemical, refining, power, offshore, pulp and paper and different amenities with in depth sizzling processes and piping techniques are frequently challenged with performing all the necessary coatings maintenance work solely during periods of outages. Outages are required in order that process equipment could be correctly maintained and repaired together with cleaning of pipelines and vessels, upkeep and replacement of pumps, motors and valves, upkeep coating operations, and different work that can only be completed when the operations are shut down.
When coatings work must be carried out on areas where elevated temperatures are involved, many suppose that the ability must be shut down. This may not be the case.
A question regularly posed by facility managers is, “Can I do maintenance painting work whereas the plant is operating?” As described under, the answer is, “Yes you can, however there are safety and health issues that have to be considered”.
Dangers to personnel must be managed no matter when or the place work is carried out.
Safety and well being considerations
There is a range of security and well being hazards that should be thought of on each industrial upkeep portray project, whether the coating materials is being applied to sizzling metal or not. Some of those include correct material handling and storage, fall safety, control of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and other health risks.
These risks must be properly evaluated and managed on each industrial upkeep portray challenge, regardless of when or the place the work is performed. While current on any job, when making use of specialty coatings to scorching surfaces, some safety and health points should obtain extra consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and type flammable mixtures in the air, particularly when atomized throughout spray utility or heated. The degree of hazard is dependent upon the following:
The auto ignition temperature (AIT) of the coating materials is the one most necessary concern when applying coatings to sizzling operating equipment. AIT is outlined (by the National Safety Council publication Accident Prevention Manual For Business and Industry: Engineering & Technology) as “…the minimal temperature at which a flammable gas-air or vapour-air mixture will ignite from its own warmth source or contact with a heated surface without the presence of an open spark or flame.”
The concept of flash point as defined by NFPA 30 is “the minimal temperature of a liquid at which sufficient vapour is given off to form an ignitable combination with the air, close to the surface of the liquid”. In different phrases, the flash point describes the temperature of the liquid that’s high enough to generate sufficient vapour to create a flame if a supply of ignition were introduced.
For vapours of flammable liquids, there’s a minimal concentration beneath which the unfold of the flame doesn’t occur when involved with a supply of ignition. This is the Lower Flammable Limit (LFL). There is a most concentration of vapour in the air above which the unfold of the flame does not occur. This is the Upper Flammable Limit (UFL). The flammable range is between the LFL and the UFL, when the focus of vapours can assist combustion.
If safety procedures are followed, outages will not be required while maintenance is carried out.
Implementing controls
Applying coatings to sizzling surfaces will increase the rate at which the solvents are pushed off. When making use of solvent borne coatings to hot surfaces it must be assumed that the focus of vapours within the air may exceed the LFL (at least for a short time after application). As with coating application to ambient temperature metal, controls must be implemented.
While the LFL is more doubtless to be achieved over a shorter period of time throughout hot application of coatings than coatings work carried out at ambient circumstances, the ensuing hearth hazard exists in each applications. That is, the hearth hazard and related controls must be considered for the appliance of any solvent-borne flammable coating system, regardless of the work environment. It should be recognized that the gas element of the hearth tetrahedron will be current in each ‘hot’ and ‘ambient’ environments and basic steps should be taken to reduce pointless solvent vapours in the work space. In addition, as outlined later, attention must even be directed to eliminating the remaining element of the tetrahedron – the source of ignition.
Controlling flammable vapours
The fuel component of a fireplace could be decreased by implementing basic controls corresponding to dealing with and storing flammable liquids in accredited, self-closing containers, maintaining the variety of flammable liquids containers within the work space and in storage areas to the minimal needed and inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate may be substituted, adopted by floor washing with recent water or steam cleaning and pH testing of the floor, or non-combustible solvents corresponding to 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gasoline indicators must be used to verify that the focus of flammable vapours is below the LFL. Combustible fuel indicators must be calibrated in accordance with the manufacturer’s recommendations and have to be approved to be used in flammable atmospheres. Operators of the gear must be skilled in proper equipment operation.
Readings should be taken in the general work space and the vicinity of the operator and in areas the place there are potential sources of ignition. Typically, items are set to alarm at 10% of the LFL. If the alarm sounds, coatings utility work ought to instantly stop until the concentration of flammable vapours is managed. The function of setting the alarm under the LFL is to supply a security factor that results in control measures being carried out earlier than there is an imminent danger of fire or explosion.
Monitoring of the flammable vapour concentration shall be essential as the effectiveness of natural ventilation may be variable. If control of flammable vapours requires mechanical ventilation, an occupational security or health skilled or engineer with experience in industrial air flow ought to be consulted.
At a minimal, mechanical air flow techniques ought to present enough capacity to manage flammable vapours to under 10% of the LFL by both exhaust air flow to remove contaminants from the work area or by dilution air flow through introduction of recent air to dilute contaminants. As with combustible fuel indicators, air flow tools should be approved for protected use in flammable atmospheres. In addition, ventilation gear must be grounded and bonded.
Additional ventilation, if needed, should be steady throughout coatings utility as concentrations might improve as more surfaces are coated in the course of the course of a work shift, and particularly on scorching surfaces where the rate of vaporization is larger.
Ventilation during coatings utility ought to be continuous, especially when engaged on sizzling surfaces.
Sources of Ignition
When applying coatings to hot surfaces, the first supply of ignition that readily involves thoughts is the heat from the surface being painted. The AIT of the coating material is the one most necessary issue when applying coatings to hot operating gear. The AIT of a substance or mixture is the minimum temperature at which a vapour-air mixture will ignite when in contact with a heated surface, with out the presence of any open spark or flame.
The key to controlling this source of ignition is to confirm the surfaces being coated are beneath the AIT of the coatings being utilized. While surface temperatures could additionally be known/available in lots of amenities, all floor areas of the process/piping being painted and/or any tools adjacent to the gadgets being painted the place overspray may deposit ought to be measured for precise floor temperature. The results must be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily apparent, a extra refined however nonetheless critical supply of ignition to regulate on any industrial painting venture involving flammable solvents involves the production of static electrical energy. Equipment related to the spray-painting operation, similar to spray utility tools and ventilation tools, can generate static electrical energy.
In addition to external sources of ignition, spontaneous ignition can happen when rags or wastes soaked with paint solvents are left in open containers. จำหน่ายเกจวัดแรงดัน happens when the sluggish technology of heat from oxidation of natural chemicals corresponding to paint solvents is accelerated till the ignition temperature of the gasoline is reached.
This condition is reached when the material is packed loosely permitting a big floor space to be uncovered, there’s sufficient air circulating across the material for oxidation to happen, however the pure ventilation available is inadequate to carry the warmth away quick sufficient to prevent it from build up.
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